The present invention relates to an apparatus for random number generation comprising a feedback shift register which receives signals from a first signalling device, the feedback shift register being connected to at least one clocked delay device which upon receiving a clock signal from a second signalling device produces a random number. Such devices find their use within e.g. radiocommunication, for production of crypto-keys etc. The requirements are that random numbers, both random numbers produced by one and the same apparatus as well as random numbers produced by different apparatuses are as uncorrected and unpredictable as possible.
There is furthermore often a need of a random number generator which may be integrated in an LSI (Large Scale Integration)-circuit.
An apparatus of the abovementioned kind is given by U.S. Pat. No. 4,905,176. In this known apparatus On-Chip noise- sources are used as a first signalling device. Such On-Chip noise sources are both difficult and expensive to fabricate. Moreover they consume much current. Furthermore the random numbers which are generated by this apparatus do not originate from external events but depend on parameters of the LSI such as for example material and constitution, the circumstances prevailing at its fabrication and so on. Since the random numbers come directly from the outputs of a large PN-register, different apparatuses which are started up and driven simultaneously will generate the same random number. Moreover, different inputs from the same PN sequence are used as the input to the logical gate (XOR). A further inconvenience with this apparatus is that the random numbers merely can be obtained in series and not in parallel.
In other known apparatuses noise diodes are used which generate noise which is amplified and quantified. In this manner generated random numbers are read by a computer. Random number generators of this kind require a large number of discrete and integrated components and it is furthermore not possible to integrate the whole random number generator in an LSI. Furthermore these apparatuses require high voltages, such as approximately 20 V as well as high currents, e.g. more than 50 mA.